Where Did The Horseweed Go?
DR. LARRY STECKEL
JACKSON, TENN.
Where is the horseweed (marestail)? That has been a common question this March. I have no data to say exactly but I can speculate. My thought is that the main event that has limited its germination was the very dry fall and indeed winter of 2016 and 2017.
So are we out of the woods with respect to horseweed being a problem? The answer would be no as I expect we will get a good bit of horseweed germination after the wet/cold snap. That being said, with all the new herbicide trait technologies being planted this spring horseweed should be less of an issue for at least the next few years. Liberty on a warm day and the higher rates of dicamba and 2,4-D in-crop should effectively remove horseweed in LL, Xtend or Enlist traited crops.
So will horseweed be out permanently as a major weed problem? Probably not, as it has shown the ability to overcome most any herbicide if that is the main tactic used to control it. However, if we rotate the herbicides used in the traited crops as well as rely more on cultural practices like cover crops we should at least be able to delay new herbicide resistance developing in horseweed. ∆
DR. LARRY STECKEL: Extension Weed Specialist, University of Tennessee